Bird’s-Eye
View of the Amazon
Airborne Archaeologist Challenges the Myth of a Pristine Wilderness

by Ted Mann

In
the office of a typical archaeologist, you would expect to
find things like stone tools, pottery fragments, and maybe
even a few Wooly Mammoth bones. But Clark
Erickson is no typical archaeologist. Oversize rolls
of aerial photographs are stacked into tubular pyramids on
a desk and worktable in his University Museum office. They
fill up file cabinets and populate a storage room. At last
count, he had about 700 giant aerial and satellite images—almost
all of them picturing some region of the Amazon.

He rolls out a 1958 U.S. Air Force photo of a Bolivian savannah.
Even with the vast acreage blown up to movie-poster size,
the details are as impenetrable as braille to the sighted. “See
that,” he says, pointing to a line running across the
landscape. “Anything that’s straight—it’s
not natural.” With a finger, he traces a symmetrical
block of toothpick shapes. “These are raised fields.
See, you can pick out the linear patterns.” With Erickson’s
narration, more and more geometric designs pop off the glossy
print—settlement mounds, fish weirs, irrigation canals,
roads. The photo begins to look like a prehistoric engineering
blueprint. Unlike most archaeologists, Erickson doesn’t
begin his research in excavated holes; he starts in the sky,
reading the landscape for markers of vanished civilizations.

For the past decade, Erickson has used aerial images—borrowed
from the military, scientists, and even oil companies—to
guide his fieldwork. What he’s discovered about the
prehistoric Amazon challenges many textbook teachings. Before
Columbus, he argues, the area was heavily populated and agriculturally
advanced. His work has led to a surprising supposition: Humans
may have engineered nearly every aspect of the
Amazon landscape.

As an undergraduate, Erickson wasted no time becoming an
archaeologist. He was part of an excavation on the first
day of freshman-year classes and then spent two summers at
digs on Lake Titicaca in South America. The biggest discovery
of his young career came at the end—in the rear-view
mirror of a beat-up Volkswagen bus. The team was departing
on a five-hour drive back to “civilization.” On
an unpaved, uninhabited stretch of road, cresting over a
ridge, Erickson stole one last glance at the diminishing
lakebed. Through the cracked windows, he couldn’t believe
what he saw: an unnatural crosshatch pattern. It covered
several square miles, and it seemed to be human-made.

In this part of the Amazon, farming is difficult. The soil
spends half the year scorched in desert heat and the other
half inundated with rain. For this reason, say scholars,
the region is incapable of sustaining large civilizations.
Erickson believes the raised fields he glimpsed through the
back window of his microbus were a solution hit upon by an
ancient people. The system of mounds and canals provided
irrigation in the dry season and drained the soil during
floods. Ten years before, geographer William Denevan had
written about the fields, but by the 1970s, when Erickson
was there,
no archaeologist had studied them. No one knew the age of the structures, who
built them, or if they even worked.

By the time Erickson earned a Ph.D., he was itching to return.
But as he hiked the dirt roads in search of the earthen structures
he’d glimpsed before, the ancient fields seemed to
have disappeared. From that point on, he says, “I vowed
never to set foot on the landscape without having studied
aerial photographs first.” Now he rents a $300-an-
hour Cessna, and a team of three students helps him photograph
the sites from every angle.

With aerial images, Erickson rediscovered the missing raised
fields, and he immediately began analyzing them. Subsequent
digs proved that the mounded fields date back to about 100
B.C. and may have been cultivated until A.D. 1100. The dimensions
of the rectangular plots were astounding: Each row rose three
feet high, measured up to 30 feet wide, and stretched 1,300
feet long. Between the rows were canals, also 30 feet wide
and three feet deep.

As much as he learned about the fields, he kept coming back
to one nagging question: Were they productive? To answer
this, he tried a little “experimental archaeology”— recreating
ancient tools and methods in order to better understand how
the raised fields worked. With help from colleagues and local
farmers, he built a field from scratch and worked it year-round. “We
found that productivity was three to four times traditional
practices like slash-and-burn,” he reports.

The more time Erickson spent in South America, the more
he kept running into, and collaborating with, a group of
sympathetic researchers, including Denevan and anthropologist
William Balée. Together, the three men challenged
conventional thinking about the Amazon. To begin with, they
dismissed “the pristine myth” that the Americas
before Columbus were an untouched Eden. Denevan countered
that, in fact, much of the Amazon is anthropogenic—human
made—and the sheer number of engineered earthworks
and their size, he concluded, would have required a massive
workforce.

Looking at an aerial photo of the Baures region of Bolivia,
Erickson’s index finger dances between dark polka dots
covering bare earth. These, he notes, are forest islands
and mounds that can rise 60 feet above the savanna. Causeways
radiate from them like spokes on a wheel. Erickson and Balée
have shown that the mounds were once settlements, housing
between 500 and 1,000 inhabitants. Beneath the canopies of
the island forests, the two men discovered pottery, bones,
and orchards of fruit trees. The dozens of raised causeways,
however, still leave Erickson scratching his head. Most are
straight as a ruler, stretching from mound to mound. “It
looks like everyone in the society had their own road and
used it once!”

For all the evidence that Erickson and his colleagues have
offered, there is still resistance to the idea of a once
populous Amazon. Old-school anthropol-ogists, like the Smithsonian’s
Betty Meggers, hold that the region’s aluminum-rich
soil couldn’t have supported the agricultural base
a large civilization needs to thrive. Environmentalists push
the “pristine myth” and, Erickson fears, often
see his work as “some excuse that we’re giving
developers to go and rape the Amazon.” Even natural
scientists abhor the new anthropocentric view of the Amazon. “When
I give talks at the Field Museum in Chicago, there is always
a bunch of them literally yelling at me.” Meggers went
so far as to claim, in the journal Latin American Antiquity,
that “the myth of El Dorado is being revived by archaeologists.”

In an ironic twist, the lost gold of El Dorado may turn
out to be that oft maligned soil. In the 1990s, geologists
began examining Amazonian earth, and though much was inhospitable,
large swaths turned out to be fertile. Called Amazonian Dark
Earth, or terra preta by locals, this near-black soil has
amazing properties. Dark Earth retains its nutrients during
tropical rains, while other soil is leeched, and like potting
soil, it is far more productive for growing crops. The trait
that makes it so exceptional, and enigmatic, is its ability
to regenerate. Locals quarry and farm the rich soil, and
their supply always grows back. Dark Earth re-creates itself
atop a base layer and grows—just like a living organism.

Scientists are still analyzing the biology, but Erickson
believes the Amazon Indians enriched their earth with a microorganism,
one that resisted depletion and helped fertilize. If better
understood, this process of inoculating poor soil with a
bacterial booster could aid parts of the undeveloped world
starved for agriculture. Recently, geographers estimated
that the creators of this ancient technology managed to terraform
at least 10 percent of Amazonia—an area the size of
France. Along with the raised fields, fish weirs, causeways,
and other anthropogenic features, Dark Earth may in fact
be one of countless footprints left by a lost civilization.
Indeed, if Erickson is right, the Amazon could be humankind’s
largest engineering relic.